You have settled in France since Brexit, and now you are selling the house you kept in Manchester, Bristol or London. The sale completes, the money lands in your account, and then the worry starts: will the French tax office claim a share, will HM Revenue and Customs claim one too, and could you end up paying full capital gains tax twice on the same sale? The short answer is that both countries can indeed tax the gain, but the double tax treaty between France and the United Kingdom gives France the job of wiping out the double charge through a tax credit. The longer answer is that the relief only works if you file the right forms, in the right order, on both sides of the Channel, and inside deadlines that are brutally short. On the British side you must report the sale and pay any Capital Gains Tax within 60 days of completion. On the French side you must file a special return, form 2048-IMM, within the month following the disposal when the gain is not exempt in France. Miss either step and you face interest, penalties and a French assessment computed without the treaty credit. This guide explains where your UK house sale is taxed now that you are French resident, how the treaty credit works, how to declare the gain, and how to challenge a bill that ignores the treaty or gets the maths wrong.

I. Where your UK house sale is taxed now that you live in France

A. France taxes your worldwide gains while the United Kingdom taxes the bricks on its soil

Once you are French tax resident, France taxes you on your worldwide income and gains, including a house sitting in England. French domestic law states the rule bluntly: “Les personnes qui ont en France leur domicile fiscal sont passibles de l’impôt sur le revenu en raison de l’ensemble de leurs revenus. Celles dont le domicile fiscal est situé hors de France sont passibles de cet impôt en raison de leurs seuls revenus de source française.” In plain English, French residents pay income tax on everything they earn or gain anywhere in the world, while non-residents pay only on French-source income. Your UK house sale therefore falls inside the French net from the day your tax home, known in French as your domicile fiscal, moves to France.

Whether that day has actually arrived is often the first fight with the tax office. French law treats you as French tax resident if you meet any one of three tests: “1. Sont considérées comme ayant leur domicile fiscal en France au sens de l’article 4 A : a. Les personnes qui ont en France leur foyer ou le lieu de leur séjour principal ; b. Celles qui exercent en France une activité professionnelle, salariée ou non, à moins qu’elles ne justifient que cette activité y est exercée à titre accessoire”. Your foyer means your family home, the place where your spouse and children habitually live; your séjour principal means the country where you spend most of the year. For a British family that has bought or rented its main home in France, enrolled the children in a French school and spends most nights there, the test is met even if one spouse still commutes to London. Keep boarding passes, utility bills, school certificates and your French residence permit together from the first year, because the date your tax residence switched determines which country had first claim on the gain and which forms you owed.

Inside France, the gain on a property sale is called a plus-value immobilière, literally an increase in property value. The code draws the net very wide: “I. – Sous réserve des dispositions propres aux bénéfices industriels et commerciaux, aux bénéfices agricoles et aux bénéfices non commerciaux, les plus-values réalisées par les personnes physiques ou les sociétés ou groupements qui relèvent des articles 8 à 8 ter, lors de la cession à titre onéreux de biens immobiliers bâtis ou non bâtis ou de droits relatifs à ces biens, sont passibles de l’impôt sur le revenu dans les conditions prévues aux articles 150 V à 150 VH.” A cession à titre onéreux is simply a disposal for money, as opposed to a gift or an inheritance, so an ordinary sale of your UK house, flat or plot is caught. The starting point of the calculation is equally simple: “La plus ou moins-value brute réalisée lors de la cession de biens ou droits mentionnés aux articles 150 U à 150 UC est égale à la différence entre le prix de cession et le prix d’acquisition par le cédant.” The gross gain is the sale price minus the purchase price paid by the seller, before the various reliefs and holding-period reductions are applied.

So France taxes the gain. But the United Kingdom taxes it as well, because the house stands on British soil. This is where the double tax treaty signed in London on 19 June 2008 between France and the United Kingdom steps in. For capital gains the treaty rule is article 14, and the French tax administration explains it in its official commentary: “Aux termes du paragraphe 1 de l’article 14 de la convention, les plus-values que tire le résident d’un État de l’aliénation de biens immobiliers visés à l’article 6 de la convention sont imposables dans l’État de situation des biens.” An aliénation is a disposal, and the État de situation is the country where the property sits. A house in Leeds sold by a French resident may therefore be taxed in the United Kingdom, the country of situation, even though the seller lives in France.

That sounds like double taxation, and without the second half of the treaty it would be. The treaty does not take away France’s right to tax its own resident; it orders France to neutralise the British tax. The official commentary continues: “l’alinéa b) du paragraphe 4 de l’article 24 prévoit que lorsque des gains peuvent être imposés par un État contractant qui n’est pas l’État de résidence du cédant en application des dispositions des paragraphes 1, 2 et 3 de l’article 14, c’est à l’autre État contractant, État de résidence du cédant, et non au premier État contractant, qu’il revient d’éliminer la double imposition.” The cédant is the seller. In your case the seller’s residence state is France, so France must eliminate the double charge. For a house sale the credit equals the British tax: “Le crédit d’impôt est égal, pour les cessions portant sur des biens immobiliers ou des sociétés, partnerships ou trusts à prépondérance immobilière, à l’impôt britannique et, pour les autres cessions, à l’impôt français, à condition que le résident de France soit effectivement soumis à l’impôt britannique à raison de ces gains.” A crédit d’impôt is a tax credit subtracted from your French bill. The French tax office puts the same mechanism in everyday language: “Lorsqu’une convention fiscale est signée, elle prévoit en principe que les plus-values réalisées lors de la cession d’immeubles sont imposables dans l’État où les immeubles sont situés.” And on the amount of relief: “Il est alors possible de déduire un crédit d’impôt du montant de l’impôt français. Ce crédit d’impôt est déterminé selon les termes de la convention : il est égal au montant de l’impôt français calculé sur cette plus-value ou à l’impôt étranger sans dépasser le montant de l’impôt français.” Take the logic in three steps. First, France computes its own tax on the gain under French rules. Second, you prove the British tax you actually paid on the same gain. Third, France subtracts a credit equal to the British tax, capped at the French tax, so you never pay more than the higher of the two bills on that gain. If the British bill is higher than the French computation, the surplus is not refunded; if the French computation is higher, you pay France the difference. Either way you do not pay twice.

Two practical consequences follow. First, always pay the British tax properly and keep the proof, because without British tax actually charged there is nothing to credit. Second, always declare the gain in France even when you expect the credit to wipe the French bill to zero, because the credit is granted through the French return, not automatically.

B. Recent movers face a six-year British shadow, and non-resident rules do not protect you

If you moved to France recently, a second treaty provision can extend the British claim well beyond the house itself. The official commentary warns: “Le paragraphe 6 de l’article 14 de la convention permet à un État contractant d’imposer, en vertu de son droit interne, les gains tirés de l’aliénation de tout bien réalisée par une personne qui, à un moment quelconque de l’année fiscale au cours de laquelle le bien est aliéné, ou à un moment quelconque pendant les six années fiscales précédentes, est, ou a été, résident de cet État contractant.” In other words, the United Kingdom may tax gains on any asset, not only houses, realised by someone who was British resident at any point in the tax year of sale or the six previous tax years. This catches the classic post-Brexit pattern: you relocate to Lyon in 2024, keep a portfolio of shares or a second property, and sell in 2026. London can still raise a bill under its domestic rules for former residents.

For your UK house the analysis stays favourable, because the house is also covered by the situs rule in article 14, paragraph 1, and in that combined situation it is France that eliminates the double charge, as shown above. But the six-year rule matters for everything else you sell after the move, and it reverses the machinery: “En revanche, lorsque les gains réalisés par un résident de France sont susceptibles d’être imposés par le Royaume-Uni sur le seul fondement du paragraphe 6 de l’article 14 de la convention, il appartient au Royaume-Uni, et non à la France, d’éliminer la double imposition, selon les modalités prévues par les paragraphes 1 et 2 de l’article 24 de la convention.” When London taxes only as the former residence state, London must give the relief. Map every disposal in the first six years after your move against both provisions before you file, and take coordinated advice in both countries rather than assuming the house logic covers shares, stock options or crypto-assets.

A related confusion must be cleared up, because it produces expensive mistakes. British owners often hear about the French levy on non-residents, the prélèvement, and assume it covers their UK sale. It does not. The levy is defined for people outside the French net selling French property: “I. – 1. Sous réserve des conventions internationales, les plus-values, telles que définies aux e bis et e ter du I de l’article 164 B, réalisées par les personnes et organismes mentionnés au 2 du I lors de la cession des biens ou droits mentionnés au 3 sont soumises à un prélèvement selon les taux fixés au III bis.” An un prélèvement here is a flat-rate withholding-style levy collected at the notaire’s desk. Once you are French tax resident, you are no longer in that category for your UK house: you are taxed under the ordinary resident rules with a treaty credit, not under the non-resident levy. The same switch applies in reverse to a French house you kept: as a French resident you sell it under the standard plus-value immobilière rules, not under the non-resident levy. Anyone who files a UK house sale on a non-resident form, or who lets a French notaire apply non-resident logic to a resident seller, is filing in the wrong lane, and the assessment that follows will be wrong from the first line.

II. How to declare the sale and how to challenge an unfair bill

A. File on both sides of the Channel in the right order and inside the deadlines

Start with the British clock, because it runs fastest. The British government requires: “You must report and pay any Capital Gains Tax due on UK residential property within 60 days of completing the sale of the property.” Completion means the day legal ownership transfers, not the day you accept an offer or exchange contracts. The warning attached is explicit: “You may have to pay interest and a penalty if you do not report and pay on time.” File through the UK capital gains on property account, pay the estimated British tax, and keep the submission receipt and payment confirmation. Those two documents are the foundation of your French credit claim. Note that the 60-day return is separate from your ordinary UK Self Assessment return; one does not replace the other, and a sale with no British tax due can still carry a reporting obligation, so check the position for your exact facts rather than assuming silence is safe.

Turn next to the French filing. The French tax office instructs residents selling property abroad: “Si vous avez réalisé une plus-value hors de France métropolitaine ou des départements d’outre-mer et que ce revenu n’est pas exonéré d’impôt en France en application d’une convention fiscale internationale, il faut déposer dans le mois qui suit la cession, auprès du service des impôts dont vous relevez” “en cas de cession d’un immeuble, une déclaration n° 2048-IMM.” A service des impôts is your local French tax office, and the 2048-IMM is the special capital gains return for property disposals. Because your UK house gain is taxable in France with a credit, not exempt, the 2048-IMM within the month after the sale is in principle due. The same official page gives the mirror case: “Si la plus-value réalisée à l’étranger est exonérée d’impôt en France, vous ne devez pas souscrire de déclaration n° 2048 en plus du formulaire n° 2047”, the 2047 being the return for income received abroad. Work out before completion which lane you are in, so the one-month clock does not catch you unprepared.

Behind those forms sits your ordinary annual obligation. French law requires every taxable person to file a detailed yearly return: “1. En vue de l’établissement de l’impôt sur le revenu, toute personne imposable audit impôt est tenue de souscrire et de faire parvenir à l’administration une déclaration détaillée de ses revenus et bénéfices, de ses charges de famille et des autres éléments nécessaires au calcul de l’impôt sur le revenu”. Your UK gain therefore also appears on your yearly French income tax return, with the foreign tax credit claimed there. The practical order that keeps the credit intact is: complete the UK sale, file and pay the British 60-day return immediately, file the French 2048-IMM within the month, then report the gain and claim the credit on the annual return with the British payment proofs attached. Doing it backwards, declaring in France before the British tax is assessed and paid, invites the tax office to compute French tax with no credit and to chase you for the full amount.

The French computation itself can still shrink the bill before the credit. French domestic reliefs apply to the gain because France taxes it under its own rules first. The starting point remains the sale price minus the purchase price, and the major reliefs depend on how the property was used and how long it was held. If the UK house was genuinely your main home on the day of sale, French law exempts the gain: the code carves out “1° Qui constituent la résidence principale du cédant au jour de la cession”, property that is the seller’s main residence on the day of disposal. The official public-service site confirms in its English pages that the dwelling must be your main residence at the time of sale for full exemption. For a British family that moved to France and sells the old UK home months later, that condition will usually fail, which is precisely why the next reliefs matter. Property held for a long time earns taper relief: “Vous êtes exonéré d’impôt sur la plus-value immobilière pour tout bien détenu depuis plus de 22 ans.” And the social levies, the prélèvements sociaux added to the income tax on the gain, fall away after an even longer hold: “La plus-value réalisée lors de la vente d’un bien détenu depuis plus de 30 ans est aussi exonérée de prélèvements sociaux.” A house bought in 1998 and sold in 2026 therefore faces a very different French computation from a flat bought in 2021. Reconstruct the purchase price, the purchase deed, and the exact acquisition date before you file, because the tax office will not apply reliefs you cannot evidence.

One more trap deserves a sentence. Some sellers assume that letting the UK house for a year or two after the move changes nothing. It changes the exemption picture completely, as the next section shows through a 2026 court decision, and rental periods also complicate the British side. Keep the sale, the letting history and the residence timeline in one file, and make every adviser work from the same dates.

B. Challenge the assessment when the treaty or the maths is wrong

French assessments on foreign property sales go wrong in predictable ways: the tax office treats you as resident from the wrong date, ignores the treaty credit, caps the credit incorrectly, forgets holding-period relief, or taxes you under the non-resident levy by mistake. Each of these is challengeable, and the first illustration comes from a courtroom in Nice. On 2 July 2026 the third civil chamber of the Nice judicial court, case number 24/01760, condemned a firm of notaires to compensate a seller who lost the main-residence exemption: “l’article 150 U, II, 1° du code général des impôts prévoit une exonération d’impôt sur la plus-value immobilière lorsque le bien cédé constituait la résidence principale, effective et habituelle du vendeur et était occupé par lui au moment de la vente ; en revanche il n’y a pas d’exonération si le vendeur a quitté les biens immobiliers objet la cession avant celle-ci, et s’ils étaient loués et occupés par un tiers.” A résidence principale effective et habituelle is a real, everyday main home actually lived in, not a paper address. The seller had moved out and the property was let to someone else at the sale, so no exemption; the notaires, state-appointed conveyancing officers who owe clients a duty of advice and verification, had failed to secure the position and were ordered to pay 18,655 euros for the financial loss, 1,500 euros for moral harm and 2,500 euros under article 700 of the civil procedure code, the costs provision. For a British seller the moral is direct. If you moved to France, let the UK house, then sold it, neither France nor common sense treats it as your main home at sale. Structure the calendar deliberately: understand from day one whether you are selling a former main home with residual reliefs or a let investment with none, and put that analysis in writing with your notaire or conseil before the completion date, not after the assessment arrives.

When the assessment itself is wrong, French procedure gives you a two-stage remedy. First comes the formal complaint to the tax office, called a réclamation contentieuse: “Les réclamations relatives aux impôts, contributions, droits, taxes, redevances, soultes et pénalités de toute nature, établis ou recouvrés par les agents de l’administration, relèvent de la juridiction contentieuse lorsqu’elles tendent à obtenir soit la réparation d’erreurs commises dans l’assiette ou le calcul des impositions, soit le bénéfice d’un droit résultant d’une disposition législative ou réglementaire.” L’assiette is the taxable base and le calcul is the arithmetic, so a credit forgotten, a credit capped at the wrong figure, a residence date misread or a levy applied to a resident all fit squarely inside this complaint. File it in writing with the office that issued the assessment, attach the completion statement, the British 60-day filing receipt, the British payment proof, the French 2048-IMM and the annual return, and ask explicitly for the treaty credit under article 14 and article 24 of the France–United Kingdom treaty with a recalculation. Second, if the administration rejects the complaint in whole or in part, you can go to court: “En matière d’impôts directs et de taxes sur le chiffre d’affaires ou de taxes assimilées, les décisions rendues par l’administration sur les réclamations contentieuses et qui ne donnent pas entière satisfaction aux intéressés peuvent être portées devant le tribunal administratif.” The tribunal administratif is the first-instance administrative court for direct taxes. Both stages run under strict time limits that start from the assessment or the rejection letter, so diary them on receipt and do not wait for a reminder that will never come.

Frame the complaint around one of four arguments, in this order. First, residence timing: prove with the article 4 B evidence that you were French resident at the sale date, which switches the case from the non-resident levy to the resident-plus-credit regime. Second, treaty title: cite article 14, paragraph 1 for the shared taxing right and article 24, paragraph 4 for France’s duty to eliminate the double charge. Third, credit maths: show the British tax actually paid, convert it at the correct rate, and demonstrate the cap computation line by line. Fourth, domestic computation: verify the gross gain under article 150 V, the acquisition date, and any holding relief before the credit is applied, because an inflated French base inflates even a correctly credited bill. Most files win or lose on documents rather than doctrine, so keep every deed, transfer confirmation, exchange-rate slip and filing receipt for the life of the challenge plus the years the administration can still audit.

Conclusion

Selling your UK house after settling in France does not mean paying full tax twice, but it does mean satisfying two tax systems that move at different speeds. France taxes the gain as part of your worldwide income, the United Kingdom taxes it because the bricks stand on its soil, and the treaty makes France erase the overlap with a credit equal to the British tax, capped at the French tax on the same gain. Recent movers should also watch the six-year British shadow over their other assets. File the British 60-day return and pay first, file the French 2048-IMM within the month, declare everything on the annual return with the British proofs, and check the French computation for residence dates, holding relief and credit maths before you accept it. If the assessment ignores the treaty or miscalculates the credit, complain in writing and, if needed, take the case to the administrative court. Handled in that order, a UK sale funds your French life instead of funding two treasuries.

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